In the aforedescribed copending applications and the earlier applications and patents mentioned therein, there are described flow-direction-change particle separators which operate on inertial principles and wherein the particles entrained by the gas stream are collected in collection or phase-separation chambers formed on corrugated plates which define flow passages for the gas stream between them. Reference may also be had to German published application (Auslegeschrift) DT-AS 22 51 173.
In systems of the aforedescribed type a multiplicity of generally vertically oriented plates define flow passages between them for a gas stream entraining the particles to be recovered, these particles generally being solid or liquid particles, e.g. liquid droplets.
The plates are provided with corrugations which can run vertically and the crests and/or troughs of these corrugations may be formed with phase-separating chambers. The corrugations, generally of trapezoidal cross-section, induce direction changes in the incoming gas stream and the phase-separating or collection chambers have gaps open toward the oncoming gas flow into which the particles to be recovered are entrained by the gas stream and are collected. In the case of a liquid, the collected liquid flows downwardly through these phase-separating or collecting chambers or compartments and can be recovered at the bottom of the apparatus.
For the purposes of the present invention, the term "corrugation" will be used to indicate any undulation in the plates defining the flow passages sufficient to induce a change in direction of the gas stream traversing these passages. In other words the invention is applicable not only to systems of the aforedescribed type in which the corrugations are generally trapezoidal in cross-section or of zig-zag profile, but also to plates which have a generally sinusoidal cross-section or configuration.
In each of the aforedescribed cases, a corrugation crest is formed on one side of the separator plate while the other side is formed with a corrugation trough in the same region. Naturally, since a plurality of corrugations are provided in each plate, on each side of the plate, a trough follows a crest and vice versa. The phase-separating chambers in the systems of the present invention are generally disposed on the outer side of the plate, i.e. upon the crests. However the invention is also applicable to arrangements in which the phase-separating chambers are provided within the troughs, i.e. project from the base of the troughs.
In the conventional construction of such particle separators (see the aforementioned German published application DT-AS No. 22 51 173), the amplitude, the corrugation width and the phase-separating or collecting chamber volumes of the individual separator plates in the flow direction for successive corrugations are the same. The two corrugation widths together define the "wavelength" or pitch of the corrugations.
It has been found in practice that such systems give rise to a pressure drop which is a function of the velocity of the gas stream and for each pressure drop, there is a predetermined separating efficiency or degree of removal of the particulates from the gas.
The degree of separation is not the same for the entire range of fluid or solid particle which is normally encountered in a gas stream and has an upper limit. With higher flow velocities, previously deposited or collected liquid droplets or solid particles which are located in the phase-separating chambers are torn away with the gas stream and carried out of the phase separating chambers thereby. As a consequence, the separating efficiency or degree is limited at higher velocities of the gas.
In order to reduce such re-entrainment of the collected particulate substances, it has been proposed to provide generally U-section collecting channels which are disposed downstream of the phase chambers or collecting chambers and are disposed on a crest downstream of the gas and opening into the flow direction. Such channels serve to recover a portion of the re-entrained materials without reducing the entry gaps for the phase-separating chambers. However, such channels have been found to give rise to an increased pressure drop without a concomitant improvement in the separating efficiency. It is also not possible with such channels to raise the upper limit of the separating efficiency.